1. Field of the Invention
The present invention relates to a wire-bonding method for bonding first and second bonding points of a workpiece, and more particularly, to a method of forming wire loops.
2. Prior Art
In wire bonding, the shape of wire loop should be constant during the entire bonding process. In the currently employed method, after the wire is connected to a first bonding point, a capillary is raised and then a reverse action is performed to the capillary. That is, the capillary is moved horizontally by a small amount in a direction opposite to the second bonding point. These movements of the capillary are performed with a clamp which holds the wire opened. The Japanese Patent Application Publication ("Kokai") Nos. 57-87143 and 63-42135 disclose these methods.
However, this prior art has problems. When the bonding surface of the second bonding point (i.e., the upper surface of the lead on the lead frame) is below the bonding surface of the first bonding point (i.e., the upper surface of the die), and the first bonding point is some distance away from the edge of the die, the wire tends to come into contact with the edge of the die. This causes an "edge shorting" unless the wire loop is set high. In other words, it is necessary that the position to which the wire is raised from the first bonding point is high.